This invention relates to analog signal processing, and more particularly, to digital processor controlled radio systems.
This invention further relates to the transceiver and components thereof described and claimed in the following U.S. patent applications filed of even date with and assigned to the asignee of the present invention: U.S. Ser. No. 791,264 entitled "An Electronic Phase Locked Loop" by Michael J. Cochran; U.S. Ser. No. 791,611 entitled "A Digitally Transmitting Transceiver" by Edward R. Caudel and William R. Wilson; U.S. Ser. No. 791,629 entitled "A Clarifying Radio Receiver" by Michael J. Cochran and Edward R. Caudel; U.S. Ser. No. 791,449 entitled "An Automatically Clarifying Radio Receiver" by Michael J. Cochran and Edward R. Caudel; U.S. Ser. No. 791,450 entitled "A Transceiver With Only One Reference Frequency" by Michael J. Cochran; U.S. Ser. No. 791,265 entitled "A Signal Strength Measuring Transceiver" by Edward R. Caudel; U.S. Ser. No. 791,614 entitled "A Charge Transfer Device Radio System" by Michael J. Cochran: U.S. Ser. No. 791,253 entitled "A Transceiver Capable of Sensing A Clear Channel" by Jerry D. Merryman, Michael J. Cochran and Edward R. Caudel; U.S. Ser. No. 791,616 entitled "A Dual Processor Transceiver" by Edward R. Caudel, William R. Wilson and Thomas E. Merrow. Such copending patent applications are hereby incorporated herein by reference. Radio systems receive radiated electronic input signals comprised of a plurality of non-overlapping frequency bands, filter one of the bands from the plurality, frequency shift the one band from radio frequencies to lower frequencies, and convert the selected band to audible sounds. The input signals may be amplitude modulated (AM), or single sideband (SSB) signals as an example. Antenna means receive the radiated input signals. Conventionally, filtering devices are included in the radio system to select one of the bands from the plurality, and mixing devices are included to frequency shift the selected band. Demodulator devices are also included to demodulate the selected band.
The radio system herein described includes a computer controlled charge transfer device to selectively filter both single sideband input signals and AM input signals. This filtering is performed by a charge transfer device filter having passbands whose bandwidth and location in the frequency domain are dependent upon the frequency of the filter's clocking signal. When the charge transfer device filter is clocked with one frequency, it passes AM signals; and when it is clocked with another frequency, the filter passes single sideband signals.
The system herein described further includes clocking means having outputs coupled to generate the filter's clocking signals. The clocking means has inputs coupled to receive digital microcommands which identify the selectable frequency of the filter clocking signal. The clocking means interprets the microcommands, and in response thereto, generates filter clocking signals of the identified frequency.
A digital processor is also included in the disclosed radio system. The digital processor has outputs coupled to the clocking means for sending the microcommands thereto. As a result of this architecture, the disclosed radio system is highly flexible. That is, it has the advantage of having no hard-wired control circuitry. And thus, the digital processor is capable of receiving a variety of manually activated input signals specifying various operating modes, of interpreting the input signals via a flexible program, and of sending the microcommand to the clocking means in a manner which implements the specified operating mode.
The disclosed radio system further includes mixing means for frequency shifting the input signals and output signals of the charge transfer device filter. The amount of this frequency shift is dependent upon the frequency of the mixers' clocking signals; and the mixer clocks are also generated by the clocking means in response to microcommands from the digital processor which may comprise a microprocessor. Thus, this architecture further increases the flexibility of the system since the digital processor has control of both the frequency shifting and frequency filtering within the system.
Another advantage of the present invention is that the control circuitry is centralized. As a result, the filter means, the clocking means, and the digital processor means are each clearly identifiable entities. Such modularization is desirable for ease in fabrication and maintenance. As an example, the filter means or clocking means is capable of being checked out separately before being integrated into the radio system.
Accordingly, it is one object of the invention to provide an improved radio system.
Another object of the invention is to provide a radio system having flexible centralized control circuitry.
Another object of the invention is to provide a radio system having filter passbands which are selectable by microcommands from a digital processor.
Another object of the invention is to provide a radio system having mixers which frequency shift signals in response to microcommands from a digital processor.
Still another object of the invention is to provide a radio system which is modular for ease in fabrication and maintenance.